1. Field of the Invention
The present invention relates to a switching-device remaining lifetime diagnosis method in which the remaining lifetime of a switching device is diagnosed based on the performance characteristics of the switching device and to a remaining lifetime diagnosis apparatus utilizing the remaining lifetime diagnosis method.
2. Description of Related Art
In general, a switching device such as an electric power switching device (simply referred to as a switching device, hereinafter) is provided with a fixed contact, a movable contact that is provided in such a way as to face the fixed contact, and a driving mechanism that drives the movable contact in such a way that the movable contact comes in contact with the fixed contact or is separated from the fixed contact. The deterioration in such a switching device develops due to contributing factors such as an elapsed time from a time point when the switching device has initially started its operation, the number of operations, the time period of non-operation, and foreign materials in its moving parts; at a certain time point, the performance characteristics thereof deviate from a predetermined service condition and the remaining lifetime thereof expires. Therefore, in general, a status monitoring apparatus monitors the operation status and the like of a switching device so as to diagnose the deterioration status of the performance characteristics and the remaining lifetime.
A conventional status monitoring apparatus for a switching device periodically calculates the changing rate of the performance characteristics of a switching device, which is a monitoring subject; based on the calculated changing rate of the performance characteristics, the status monitoring apparatus estimates the time in which the performance characteristics reach a predetermined reference value or a possible number of operations (e.g., refer to Patent Document 1). In the case where deterioration in the performance characteristics of a switching device is caused by a single contributing factor and the performance characteristics of the switching device monotonously develops toward the deterioration, such a conventional switching-device status monitoring apparatus is effective for diagnosing the deterioration status of the performance characteristics of the switching device or the remaining lifetime of the switching device.    [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-149230